This application seeks to continue the Pediatric Pharmacology Research Unit at The University of Tennessee, Memphis. The continuation of the grant will further strengthen the existing multidisciplinary expertise and ongoing pediatric pharmacokinetic, pharmacodynamic, and pharmacogenetic studies within the Departments of Pediatrics and Clinical Pharmacy at The University of Tennessee, Memphis. The goals for the Pediatric Pharmacology Research Unit (PPRU) are: 1) to provide the clinical data on new and currently marketed drugs that are necessary for Food and Drug Administration approval for use in children and 2) to investigate the pharmacology of new molecular entities and biopharmaceuticals for use in children. The UT-PPRU has been actively collaborating with other Network PPRUs to generate data supporting FDA-labeling of drugs for use in children. Investigators in the PPRU are from the Departments of Pediatrics and Clinical Pharmacy at The University of Tennessee, Memphis with clinical and laboratory sites at LeBonheur Children's Medical Center, St. Jude Children's Research Hospital, and The Newborn Center at the Regional Medical Center. The pediatric clinical pharmacology programs at The University of Tennessee, Memphis have a long history of studying drug therapy in children demonstrating the committments of the University and the various clinical institutions towards clinical pharmacology research. The UT-PPRU (5th year of funding) joins the State of Tennessee Center of Excellence in Pediatric Pharmacokinetics and Therapeutics (CPPT) (13th year of funding), the Crippled Children's Foundation Research Center (5th year of funding), the NIH-funded General Clinical Research Center (36th year of funding), and the Neonatal Network (10th year of funding) as programs focused on studying basic mechanisms that underlie the relationship between drug disposition and drug effect, translating this information into improved drug therapy regimens for children, and obtaining the necessary clinical drug data to gain FDA-approval for use in children. Established areas of expertise relating to pediatric clinical pharmacology and metabolism include: 1) pharmacokinetics and pharmacodynamic drug studies, 2) pharmacogenetic studies of drug metabolism, 3) cellular regulation of Na+-dependent organic solute and drug transport in the developing nephron, and 4) amino acid regulation and metabolism in infants.